Host Factors

Fig. 3.16 Dynamic model for polyamide intervention in LSF2/YYI induction of latency. The host factor LSF (orange oval) is shown bound to the HiV long terminal repeat (LTR) and recruits YYl (green triangle) followed by HDAC...

Other host factors, which form integral components of the host innate immune arsenal, also serve to specifically inhibit HfV-l replication in susceptible cells by... 

Neuropathology of AIDS is thought be a result of complex interactions of both viral and host factors that directly or indirectly cause neuronal loss as well as other manifestations associated with neuroAIDS (Jones and Power 2006). The HIV envelope... 

Host factors can help to ensure selection of the most appropriate antimicrobial agent. Age is an important factor in antimicrobial selection. With regard to dose and interval, renal and hepatic function varies with age. Populations with diminished renal function include neonates and the elderly. Hepatic function in the neonate is not fully developed, and drugs that are metabolized or eliminated by this route may produce adverse effects. For example, sulfonamides and ceftriaxone may compete with bilirubin for binding sites and may result in hyperbilirubinemia and kernicterus. Gastric acidity also depends on... 

Etiologic microorganisms vary according to the area involved, host factors, and exposures. In otherwise healthy adults, S. aureus and GAS are the most common causative bacteria. GAS is the causative pathogen in approximatey 65% of erysipelas cases.9 0Persons who are immunocompromised, have vascular insufficiency, or use injection drugs are at risk for polymicrobial cellulitis.3... 

Host Factors Probable Etiologic Bacteria Mild Infection or Step-Down Therapy3 (Oral Antibiotic Therapy) Moderate-Severe Infection3 (IV Antibiotic Therapy)... 

There are several other host factors present that should be mentioned that inhibit what are known as bacterial virulence factors. In general, these virulence factors are mechanisms that bacteria utilize to cause infection and/or ensure their survival. 

Both microbial and host factors are important determinants in the development of osteomyelitis.2,3,9 Staphylococcus species possess bacterial adhesions, which promote their attachment to tissues and foreign devices. As such, S. aureus... 

Exogenous/Environmental Factors Endogenous/Host Factors ... 

Fauci AS. Host factors and the pathogenesis of HIV-induced disease. Nature... 

In terms of pharmacokinetics, many host factors, such as the route of administration, the metabolism, the catabolism and clearance will considerably determine the anti neoplastic success of a drug. One major difficulty with the clinical effectiveness of chemotherapy of neoplastic diseases is the requirement that it kill malignant tumor cells at doses that allow cells in the patient s vital organs to survive so that the recovery can occur. In other words, it is to obtain a reasonably safe therapeutic index favoring introduction into clinical practice. 

Other contributions to this book have taken a molecular view of parasitic nematodes, yet molecules make only a rather brief appearance here. This chapter has tried to show that parasitic nematodes are fascinatingly and tantalizingly diverse at a phenotypic level. It has focused particularly on diversity in phenotypes that are apparent in response to environmental conditions within or outside a host. The interaction of parasites with within-host factors is a major current research effort. However, helminth immunology is particularly notable for its inattention to diversity, especially when compared with the immunology of parasitic protozoa (Read and Viney, 1996). Observations of the interaction of host immunity with subsequent development in S. ratti show the potential power of such interactions. It is also clear that a principal mechanism of the action of host immune responses is against nematode fecundity (Stear et al., 1997). This is likely to be a molecularly complex interaction. Understanding this interaction, as well as variation in the interaction is interesting, but could also form the basis of control by transmission-reduction rather than eradication per se. 

This dilemma could be overcome by the hypercycle model hypercycles are in fact not theoretical concepts, but can be observed (in a simple form) in today s organisms, where an RNA virus transfers the information for an enzyme in the host cell, which is able to carry out the preferred synthesis of new virus RNA. This RNA synthesis is supported by host factors, and an RNA minus-strand is formed. The following RNA replication affords a plus-strand. The process corresponds to a double feedback loop and involves the enzyme coded by the RNA matrix and the information present in the matrix in the form of a nucleotide sequence. Both factors contribute to the replication of the matrix, so that there is second-order autocatalysis (Eigen et al., 1982). 

Riley L W, Cohen M L, Seals J E, Blaser M J, Birkness K A, Hargrett N T, Martin S M and Feldman R A (1984), Importance of host factors in human salmonellosis caused by multiresistant strains of Salmonella , Journal of Infectious Diseases, 149, 878-883. 

Diarrhea is a well-known complication of antibiotic therapy. Rates of antibiotic-associated diarrhea (AAD) vary from 5 to 25%. Some antibiotics are more likely to cause diarrhea than others, specifically, those that are broad spectrum and those that target anaerobic flora. This paper reviews the effects of antibiotics on the fecal flora as well as host factors which contribute to AAD. Clinical features and treatment of AAD are also described. Prevention of AAD rests on wise antibiotic policies, the use of probiotics and prevention of acquisition in the hospital setting. Data from clinical trials suggest that poorly absorbed antimicrobials might have a decreased risk of causing AAD and Clostridium difficile-associated disease, as concluded from studies of antibiotics used for preoperative bowel decontamination and poorly absorbed antibiotics used for traveler s diarrhea. Controlled trials would prove this but are not yet available. Probiotics may be a good adjunct to poorly absorbed antibiotics to minimize the risk of diarrhea associated with antibiotics. 

Selection of presumptive therapy considering every infected site Host factors Drug factors... 

To select rational antimicrobial therapy for a given infection, a variety of factors must be considered, including the severity and acuity of the disease, host factors, factors related to the drugs used, and the necessity for use of multiple agents. 

Other host factors are related to the necessity for surgical drainage of abscesses or removal of foreign bodies and/or necrotic tissue. If these situations are not corrected, they result in persistent infection and, occasionally, bacteremia, despite adequate antimicrobial therapy. 

Intraabdominal infections have a wide spectrum of clinical features often depending on the specific disease process, the location and the magnitude of bacterial contamination, and concurrent host factors. Patients with primary and secondary peritonitis present quite differently (Table 42-3). 

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